package com.litianhao.nowcode.util;

import org.apache.commons.lang3.CharUtils;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;

/**
 * @author litianhao
 * @create 2020-05-22 19:31
 */
@Component
public class SensitiveFilter {

    private static final Logger logger = LoggerFactory.getLogger(SensitiveFilter.class);

    //将敏感词替换成***
    private static final String REPLACEMENT = "***";

    //根节点
    private TrieNode rootNode = new TrieNode();

    //初始化树
    @PostConstruct
    public void init(){
        try(
                InputStream is = this.getClass().getClassLoader().getResourceAsStream("sensitive-words.txt");
                BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        ) {
            String keyword;
            while ((keyword = reader.readLine()) != null){
                //添加到前缀树中
                this.addKeyWord(keyword);
            }
        } catch (Exception e) {
            logger.error("加载敏感词文件失败： "+e.getMessage());
        }

    }

    //将敏感词添加到前缀树.
    public void addKeyWord(String keyword){
        TrieNode tempNode = rootNode;
        for(int i=0;i<keyword.length();i++){
            char c = keyword.charAt(i);
            TrieNode subNode = tempNode.getSubNode(c);
            if(subNode == null){
                //初始化子节点
                subNode = new TrieNode();
                tempNode.addSubNode(c,subNode);
            }

            //指针指向子节点，进入下一轮循环
            tempNode = subNode;
            //设置结束的标识
            if(i == keyword.length()-1){
                tempNode.setKeyWordEnd(true);
            }
        }
    }

    /**
     * 过滤敏感词
     * @param text 待过滤的文本
     * @return 过滤后的文本
     */
    public String filter(String text){
        if(StringUtils.isBlank(text)){
            return null;
        }
        //指针1
        TrieNode tempNode = rootNode;
        //指针2
        int begin = 0;
        //指针3
        int position =0;
        //结果
        StringBuilder sb = new StringBuilder();

        while (position<text.length()){
            char c = text.charAt(position);
            //跳过符号
            if(isSymbol(c)){
                //若指针1处于根节点,将此符号计入结果，指针2向下走异步
                if(tempNode==rootNode){
                    sb.append(c);
                    begin++;
                }
                //无论符号在开头还是中间，指针3都向下走
                position++;
                continue;
            }
            //检查下一节点
            tempNode = tempNode.getSubNode(c);
            if(tempNode==null){
                //以begin开头的字符串不是敏感词
                sb.append(text.charAt(begin));
                //进入下一个位置
                position = ++begin;
                //重新指向根节点
                tempNode = rootNode;
            }else if(tempNode.isKeyWordEnd()){
                //发现敏感词,将begin到position的字符串替换掉
                sb.append(REPLACEMENT);
                begin = ++position;
                tempNode = rootNode;
            }else {
                //检查下一个字符
                position++;
            }
        }
        //将最后一批字符串放进去
        sb.append(text.substring(begin));
        return sb.toString();
    }

    //判断是否为符号
    private boolean isSymbol(Character c){
        return !CharUtils.isAsciiAlphanumeric(c) && (c<0x2E80 || c>0x9FFF);
    }

    //前缀树
    private class TrieNode{
        //关键词结束的标识
        private boolean isKeyWordEnd = false;

        //子节点(key是下级字符，value是下级节点)
        private Map<Character,TrieNode> subNodes = new HashMap<>();

        public boolean isKeyWordEnd() {
            return isKeyWordEnd;
        }

        public void setKeyWordEnd(boolean keyWordEnd) {
            isKeyWordEnd = keyWordEnd;
        }

        //添加子节点
        public void addSubNode(Character c,TrieNode node){
            subNodes.put(c,node);
        }
        //获取子节点
        public TrieNode getSubNode(Character c){
            return subNodes.get(c);
        }
    }
}
